Electrochemical energy storage device of high specific power and electrodes for said device

ABSTRACT

The claimed invention relates to electrical engineering, and in particular to production of rechargeable electrochemical energy storage devices of high specific power. Positive and negative electrodes for electrochemical energy storage device of high specific power according to the invention comprise active element interacting with aqueous alkaline electrolyte in the process of redox charge-discharge reactions made of electron-conductive electrolytic alloy having composition M (l-x-y) O x H y , where M for positive electrode is nickel or nickel-based alloy, M for negative electrode—a metal out of the group: iron, nickel, cobalt or an alloy on the basis of a metal out of this group, x is atomic fraction of absorbed oxygen in the electrolytic alloy being within the limits of 0.01≦x≦0.4, for positive electrode preferably in the limits of 0.05≦x≦0.4, y is atomic fraction of absorbed hydrogen in the electrolytic alloy being within the limits of 0.01≦y≦0.4, for negative electrode preferably in the limits of 0.05≦y≦0.4, the said electrolytic alloy functioning simultaneously as current-carrying collector and as active material.  
     Electrochemical energy storage devices of high specific power according to three embodiments of the invention comprise at least one negative and one positive electrodes submerged in aqueous alkaline electrolyte and divided by a separator—a layer of ion-conductive but non electron-conductive material.  
     Enhancement of service life owing to increase in number of recharge cycles under conditions of elimination of ecological harmful cadmium is the technical result achieved by the invention.

TECHNICAL FIELD

[0001] The claimed invention relates to electrical engineering, and inparticular to production of rechargeable electrochemical energy storagedevices (accumulators, electrochemical capacitors) of high specificpower, designed for using them in various branches of engineering, suchas automotive industry, electrical tools, communication equipment,special electrical transport (workshop battery-operated trucks, loaders,invalid wheeled vehicles), in toys etc.

BACKGROUND OF THE INVENTION

[0002] It is well known that for many technical applications it isnecessary to have rechargeable power sources of high specific power(over 0.5 kW/kg) at a rather high specific energy (over 1 kJ/kg).Widespread accumulators of various types have high specific energy (100kJ/kg and higher) but they are not able to provide high specific power,because they possess too high internal resistance (M. A. Fetcenco et al.In 16^(th) International seminar and exhibit on primary and secondarybatteries. Mar. 1-4, 1999, Florida, USA).

[0003] Conventional capacitors (oxide-electrolytic, oxide-semiconductorand ferroelectric ones) possess high specific power (10 kW/kg andhigher) but low specific energy (less than 0.5 kJ/kg) (D. Evans. The9^(th) International seminar on double layer capacitors and similarenergy storage devices. Dec. 6-8, 1999, Florida, USA).

[0004] Combination of high specific power with relatively high specificenergy is attained in special electrochemical energy storage devices,for example, in electrochemical “double-layer” capacitors, where energyis accumulated in the form of electrostatic energy of double electricallayer on the boundary between “electrode (electron conductor) andelectrolyte (ion conductor)” (N. S. Lidorenko. Reports Acad. Sci. USSR,1974, vol.126, p.1261), in accumulators of special design, characterizedwith diminished electrode thickness (M. A. Fetcenco et al. In 16^(th)International seminar and exhibit on primary and secondary batteries.Mar. 1-4, 1999, Florida, USA), as well as in hybrid electrochemicalcapacitors (RU, Cl, 2145132),where one electrode accumulates energy inthe form of electrostatic charge of double electrical layer, like inelectrochemical double-layer capacitors, and another one—in the form ofinternal energy of electrochemical reactions products, like inaccumulators.

[0005] Electrochemical double-layer capacitors (N. S. Lidorenko. ReportsAcad. Sci. USSR, 1974, vol.126, p.1261) have positive and negativeelectrodes made as a rule of carbon materials with highly developedsurface accumulating energy in the form of double-layer charge. Storedspecific energy can be calculated by the formula used for any capacitor:

E_(sp) ^(max)=C.U²/2m,  (1)

[0006] where E_(sp)—specific energy per mass unit,

[0007] C—capacitance of the capacitor,

[0008] U—operation voltage,

[0009] m—mass.

[0010] Maximum (peak) specific power of a capacitor is determined withthe following formula:

P_(sp) ^(max)=U²/4m.R_(i),  (2)

[0011] where R_(i)=equivalent internal resistance of the capacitor.

[0012] From formulae (1) and (2) it follows that increase in specificenergy and specific power of electrochemical double-layer capacitors (atone and the same mass) is possible by means of increasing operationvoltage, increasing specific capacitance and decreasing internalresistance.

[0013] Increase in operation voltage of electrochemical double-layercapacitors is achieved e.g. by going over to anhydrous organicelectrolytes with decomposition voltage over 3 V. However, in this caseinternal resistance R_(i) grows, i.e. power decreases. Besides,anhydrous electrolytes are expensive, often toxic, fire hazardous andexplosive.

[0014] Nevertheless, electrochemical double-layer capacitors withanhydrous electrolytes find an application, achieving in their bestsamples high enough characteristics: E_(sp) ^(max)≈10 J/g, P_(sp)^(max≈)3.5 W/g and service life more than one hundred thousand cycles ofrecharge. Though high cost, fire and explosion hazards are maindrawbacks limiting possibilities for use of these capacitors.

[0015] Accumulators of special design (M. A. Fetcenco et al. In 16^(th)International seminar and exhibit on primary and secondary batteries.Mar. 1-4, 1999, Florida, USA), characterized with diminished thicknessof electrodes, have very high values of specific energy (over 20 J/g),are not expensive, use non-volatile and fire safe aqueous electrolyte,but they have comparatively low power (P_(sp) ^(max)<1W/g) and limitedservice life—at most ten thousand cycles of recharge.

[0016] The stored specific energy of an accumulator can be calculated bythe following formula:

E_(sp) ^(max)=q₀.U/m  (3)

[0017] where q₀—full charge of the accumulator at discharging by verysmall current.

[0018] At increase in discharge current the charge decreases,accumulator voltage decreases both at the first moment and duringdischarging, at first slowly, then rapidly. Usually a quick voltage dropcannot be tolerated at operation of an accumulator because ofunfavourable effect on service life.

[0019] Specific energy E_(sp) released by accumulator at discharge, aswell as its specific power P_(sp), depend on discharge current I:

E_(sp)=q(I).U_(av)(I)/m,  (4)

[0020] P_(sp)=I.U_(av)(I)/m,  (5)

[0021] where q(I)—charge,

[0022] U_(av)(I)—average discharge voltage.

[0023] To achieve high values of specific power P_(sp) it is necessaryto have high ratios I/m, i.e. high current values per mass unit of theaccumulator. It is just this reason that explains design peculiarity ofhigh-power accumulator electrodes: very small thickness of bothcurrent-carrying collectors and active material.

[0024] In hybrid electrochemical capacitors (RU, Cl, 2145132) oneelectrode (usually negative one) operates on the principle ofdouble-layer capacitor, the other (usually positive one)—on theprinciple of accumulator, therewith aqueous solution of electrolyte isused in the capacitors.

[0025] Change of voltage during discharging of a hybrid electrochemicalcapacitor takes place mainly due to discharging of double-layer carbonelectrode while potential of “accumulator” electrode changes relativelyweakly. Internal resistance R_(i) depends on both electrodes since redoxreactions proceed with over-voltage.

[0026] Due to the above circumstances, hybrid electrochemical capacitorshave discharge characteristic similar to that of capacitors and theirspecific energy and power are determined with formulae (1)-(2). Hybridelectrochemical capacitors occupy an intermediate position betweenelectrochemical double-layer capacitors and accumulators, they have highspecific power (P_(sp) ^(max)≈3,5 W/g) and energy (E_(sp) ^(max)≈10J/g), they are much cheaper than double-layer capacitors with organicelectrolyte, they are fire- and explosion-proof. Service life of ahybrid electrochemical capacitor is determined by the positive electrodeand, since the discharging charge is usually several times less than itsfull charge, the number of recharge cycles may be as high as 50-100thousand cycles. However, due to high price of high-quality carbonmaterial used in negative electrodes price of hybrid electrochemicalcapacitors is in general higher than that of accumulators.

[0027] Positive and negative electrodes for electrochemical energystorage device of high specific power are known each of which is made inthe form of backing carrying on one or both sides active elementinteracting with aqueous alkaline electrolyte of the electrochemicalenergy storage device in the process of redox reactions ofcharge/discharge (RU, Cl, 2121728).

[0028] The backing is made out of electron-conductive but notion-conductive material that is chemically and electrochemicallynon-active in the working electrolyte of the electrochemical energystorage device and functions in the electrode simultaneously as acarrying base and as a current lead to the active element.

[0029] The active element is structurally formed on the backing by meansof applying a coating of a material of initial composition includingbasic metals out of a certain group or their alloy, or an alloy of atleast one metal out of this group with one or several metals-modifiersout of the group: copper, lanthanum or lanthanides, molybdenum,tungsten, manganese, vanadium, titanium, tin, lead, bismuth, gallium;pore-forming metals out of the group: aluminium, zinc, alkali andalkali-earth metals or their combinations with further chemical and/orelectrochemical treatment of the coating in solutions of acids, salts oralkalis. Group of basic metals for positive electrodes: iron, nickel,cobalt, silver; for negative electrode: iron, nickel, cobalt, cadmium.As a result of this treatment there are formed at the same timehighly-developed surface of the coating (due to etching out ofpore-forming metals) and thin oxide and/or hydroxide film of activematerial on the coating surface—the film made of mono- or polymolecularcompounds on the interphase boundary “electrode-electrolyte”. Thus, theformed active element constitutes a highly-porous electron- conductivelayer with large true surface area coated with electron-nonconductiveoxide and/or hydroxide film. The said film and the porous coating onwhich the film is located form two functionally and structurallyindependent components (phases) of active element, the first phasefunctioning as active material and the second phase—as current-carryingcollector. Total current supply in the electrode is carried out throughthe backing.

[0030] The said technical concepts are taken as a prototype for thefirst and second embodiments of the present invention.

[0031] The described design of electrodes of an electrochemical energystorage device in which the active material of the active element (thinoxide and/or hydroxide film) is located on the developed surface of thecurrent-carrying collector (a highly-porous layer of coating on thebacking) realizes the traditional principle of mutual arrangement of themain phases participating in current-producing reactions of electrode inthe electrochemical energy storage device, namely “electron conductor(collector)—active material (oxides, hydroxides)—electrolyte”. Due toextremely small thickness of oxide and/or hydroxide film of activematerial electrochemical reactions of charge-discharge proceed with ahigh rate which determines high operating characteristics of theelectrochemical energy storage device.

[0032] Common drawback of the known positive and negative electrodes forelectrochemical energy storage device of high specific power isinsufficient service life—at most 10,000 cycles of recharge. Besides,maximum specific characteristics of negative electrode are realized whencadmium is used as the base metal, which is an environmental hazardousmaterial.

[0033] Another electrochemical energy storage device of high specificpower is known in electrodes of which the described traditional conceptof mutual arrangement of main phases involved in current producingreactions is realized, comprising at least one negative and one positiveelectrodes submerged in aqueous alkaline electrolyte and divided by aseparator—a layer of an ion-conductive but not electron-conductivematerial. Each of the electrodes comprises an active element interactingwith electrolyte-electron-conductive coating applied on the backing, onthe developed surface of which a thin oxide and/or hydroxide activematerial film is formed taking part in charge-discharge redox reactionsof the electrode at operation of the energy storage device. Therewith,the positive and negative electrodes differ by their basic metals beingpart of coating applied on the backing. For positive electrode these aremetals of the group: iron, nickel, cobalt, silver, or their alloys, fornegative electrode—metals of the group: iron, nickel, cobalt, cadmium ortheir alloys (RU, Cl, 2121728).

[0034] This technical concept is taken as a prototype for third, fourthand fifth embodiments of the present invention.

[0035] Discharge characteristic of the electrochemical energy storagedevice by its shape lies between discharge characteristics of acapacitor and an accumulator, but more close to the latter (Example 5,FIG. 6). At discharge current I=0.5 A the electrochemical energy storagedevice discharges during about 2.5 seconds at average voltage of about 1V, then voltage quickly drops. It means that charge q (0.5)=0.5□2.5=1.25C, U_(av)=1 V. Calculation of electrodes and separator mass based ondata of examples 3-5 gives the following: mass of negative electrode is60 mg, mass of positive electrode is 150 mg, mass of a separatorimpregnated with electrolyte is approximately 17 mg, total mass being227 mg. Calculation made according to formulae (4), (5) leads to thefollowing values: E_(sp)=5,5 J/g, P_(sp)=2,23 W/g.

[0036] This shows that in the known electrochemical energy storagedevice of high specific power the problem of enhancement of specificelectrical characteristics is successfully solved at acceptable cost ofthe device due to use of electrodes of a certain design. Characteristicsof specific energy and power achieved in the prototype are well on thelevel of the best world technology. Thus the electrochemical energystorage device taken as a prototype can compete both with double-layerand hybrid electrochemical capacitors by specific energy and powergaining in price.

[0037] Drawback of the known electrochemical energy storage device ofhigh specific power is insufficient service life—at most 10,000 cyclesof recharge. Besides, maximum specific characteristics are realized inthe known electrochemical energy storage device when cadmium is used asthe base metal, which is an environmental hazardous material.

SUMMARY OF THE INVENTION

[0038] The problem being solved with the present invention is how toenhance the service life period (increase in number of recharge cycles)and exclude the ecological harmful cadmium as structural materialwithout decreasing the specific power and energy.

[0039] Essence of the claimed invention is as follows:

[0040] In the first embodiment of the invention—in the positiveelectrode intended for an electrochemical energy storage device of highspecific power which comprises active elements interacting with aqueousalkaline electrolyte in the process of redox charge-dischargereactions—the active element is made of an electron-conductiveelectrolytic alloy having composition M_((l-x-y))O_(x)H_(y), where M isnickel or nickel-based alloy, x is atomic fraction of absorbed oxygen inthe electrolytic alloy being within the limits of 0.01 to 0.4, y isatomic fraction of absorbed hydrogen in the electrolytic alloy beingwithin the limits of 0.01 to 0.4, the said electrolytic alloy functionssimultaneously as current-carrying collector and as active materialwhich is participating in the processes of redox charge-dischargereactions; atomic fraction x of absorbed oxygen in the electrolyticalloy can be preferably within the limits of 0.05 to 0.4. Theelectrolytic alloy can be obtained by means of mutual electrochemicalcathode co-deposition of a metal belonging to said M group of metals andthe oxides and/or hydroxides of the M-group. In the case when the activeelement is formed as an electrolytic deposit that is separatedmechanically, chemically or electrochemically from the conductivebacking on which it have been deposited on, then the current supply canbe carried out directly to the active element; in the case when activeelement is formed as an electrolytic deposit on one or both sides of aconductive backing which is made of material that is chemically andelectrochemically stable in the electrolyte of the electrochemicalenergy storage device, then the current supply can be carried outthrough the backing.

[0041] In the second embodiment of the invention—in the negativeelectrode—intended for an electrochemical energy storage device of highspecific power which comprises active elements interacting with aqueousalkaline electrolyte in the process of redox charge-dischargereactions—the active element is made of an electron-conductiveelectrolytic alloy having composition M_((l-x-y) O) _(x)H_(y), where Mis a metal of the group: iron, nickel, cobalt, or an alloy on the basisof one of the metals of this group, x is atomic fraction of absorbedoxygen in the electrolytic alloy being within the limits of 0.01 to 0.4,y is atomic fraction of absorbed hydrogen in the electrolytic alloybeing within the limits of 0.01 to 0.4, the said electrolytic alloyfunctions simultaneously as current-carrying collector and as activematerial which is participating in the processes of redoxcharge-discharge reactions; atomic fraction y of absorbed hydrogen inthe electrolytic alloy can lie preferably within the limits of 0.05 to0.4. The electrolytic alloy can be obtained by means of mutualelectrochemical cathode co-deposition of a metal belonging to the said Mgroup of metals and the oxides and/or hydroxides of the M-group. In thecase when the active element is formed as an electrolytic deposit whichis separated mechanically, chemically or electrochemically from theconductive backing on which it have been deposited on, then the currentsupply can be carried out directly to the active element; in the casewhen the active element is formed as an electrolytic deposit on one orboth sides of a conductive backing which is made of material that ischemically and electrochemically stable in the electrolyte of theelectrochemical energy storage device, then the current supply can becarried out through the backing.

[0042] In the third embodiment of the invention—an electrochemicalenergy storage device of high specific power comprising at least onenegative and one positive electrode which are submerged in an aqueousalkaline electrolyte and divided by a separator—a layer ofion-conductive but non electron-conductive material, each of theelectrodes containing an active element interacting with the electrolytein the process of redox charge-discharge reactions—the active element ofeach of the electrodes is made of an electron-conductive electrolyticalloy that has the composition M_((l-x-y))O_(x)H_(y), where M forpositive electrode is nickel or nickel-based alloy, M for negativeelectrode is a metal out of the group: iron, nickel, cobalt or an alloyon the basis of one of the metals of this group, x is atomic fraction ofabsorbed oxygen in the electrolytic alloy being within the limits of0.01 to 0.4, y is atomic fraction of absorbed hydrogen in theelectrolytic alloy being within the limits of 0.01 to 0.4. The saidelectrolytic alloy functions simultaneously as current-carryingcollector and as the active material participating in the processes ofredox charge-discharge reactions. For the positive electrode atomicfraction x of absorbed oxygen in the electrolytic alloy can liepreferably within the limits of 0.05 to 0.4 while for the negativeelectrode atomic fraction y of absorbed hydrogen in the electrolyticalloy lies preferably within the limits of 0.05 to 0.4.

[0043] In the fourth embodiment of the invention—an electrochemicalenergy storage device of high specific power comprising at least onenegative and one positive electrode which are submerged in an aqueousalkaline electrolyte and divided by a separator—a layer ofion-conductive but non electron-conductive material, each of theelectrodes containing active element interacting with the electrolyte inthe process of the redox charge-discharge reactions—the active elementof the negative electrode is made of an electron-conductive electrolyticalloy that has the composition M_((l-x-y))O_(x)H_(y), where M is a metalout of the group: iron, nickel, cobalt or an alloy on the basis of oneof the metals of this group, x is atomic fraction of absorbed oxygen inthe electrolytic alloy being within the limits of 0.01 to 0.4, y isatomic fraction of absorbed hydrogen in the electrolytic alloy beingwithin the limits of 0.01 to 0.4. The said electrolytic alloy functionssimultaneously as current-carrying collector and as the active materialparticipating in the processes of redox charge-discharge reactions. Forthe negative electrode the atomic fraction y of absorbed hydrogen in theelectrolytic alloy lies preferably within the limits of 0.05 to 0.4.

[0044] In the fifth embodiment of the invention—an electrochemicalenergy storage device of high specific power comprising at least onenegative and one positive electrode which are submerged in an aqueousalkaline electrolyte and divided by a separator—a layer ofion-conductive but non electron-conductive material, each of theelectrodes containing an active element interacting with the electrolytein the process of redox charge-discharge reactions—the active element ofthe positive electrode is made of an electron-conductive electrolyticalloy that has the composition M_((l-x-y))O_(x)H_(y), where M is nickelor nickel-based alloy, x is atomic fraction of absorbed oxygen in theelectrolytic alloy being within the limits of 0.01 to 0.4, y is atomicfraction of absorbed hydrogen in the electrolytic alloy being within thelimits of 0.01 to 0.4. The said electrolytic alloy functionssimultaneously as current-carrying collector and as the active materialparticipating in the processes of redox charge-discharge reactions. Forthe positive electrode the atomic fraction x of absorbed oxygen in theelectrolytic alloy lies preferably within the limits of 0.05 to 0.4

[0045] The shared inventive concept that unites the embodiments of thepresent invention is the realization of a new principle of mutualarrangement of the main phases participating in the current producingreactions of the electrodes. While in all conventional electrodes theactive material lies on the collector surface thus realizing the commonprinciple of mutual arrangement of phases: “electron conductor(collector)—active material (oxides, hydroxides)—electrolyte”, in thepresent invention the active material is inside the metal collectorbeing a part of its crystal structure and forms with it a singlephase—the phase of “active element”.

[0046] To the applicant's knowledge there is no technical conceptsidentical to the claimed ones. It allows, according to the applicant'sopinion, to draw a conclusion that the invention corresponds to the“novelty” criterion (N).

[0047] As a result of realization of the features of the invention newimportant properties of the energy storage device are achieved. The newarrangement of active material inside the metal collector brings on anumber of important consequences, which radically change the propertiesof electrodes and of energy storage devices as a whole. In particular,there is no contact resistance between the collector and the activematerial and loss of electronic contact between the collector and theparticles of active material is impossible as well as are flaking andpeeling off of the active material from the collector. All this makes itpossible to create extremely thin electrodes which is the main directionfor increasing specific power.

[0048] It is just these fundamentally new properties of electrodes thatpermit to accomplish, in the framework of the claimed embodiments, theset task of enhancement of service life (increase in number of rechargecycles) without decrease (even with increase) in specific power andenergy. In particular, absence of contact resistance “collector-activematerial” in the electrodes and low resistance of active material permitto increase specific power, impossibility of flaking and peeling off ofactive material from the collector and impossibility of loss ofelectronic contact between them permit to increase substantiallydurability of the electrodes at cyclic load, while combination offunctions of current collector and of active material in electrolyticalloy makes it possible to reduce mass of electrodes and consequently toincrease specific energy and power of the electrochemical energy storagedevice.

[0049] In the framework of the shared inventive concept that unites theembodiments of the present invention there is proposed a new andpractically useful application of the phenomenon of excessive hydrogenand oxygen absorption by electrolytically deposited metal, namely, thereare proposed electrodes with electrolytically deposited metal carryinginside its structure absorbed hydrogen and oxygen, and electrochemicalstorage devices with such electrodes.

[0050] The new principle arrangement of main phases participating incurrent producing reactions of electrode is characterized by absence ofdirect contact of oxides and/or hydroxides with the electrolyte. Atfirst sight, according to the common opinion, it can be evidence ofunfeasibility of the claimed concepts. However, in reality it is not so,the claimed concepts are quite feasible and industrially applicablewhich can be explained in the following way.

[0051] As is well known, on nickel-oxide positive electrode of alkalineaccumulators (nickel-cadmium, nickel-zinc, nickel-iron ones) thefollowing reaction proceeds:

Ni(OH)₂+OH⁻⇄NiOOH+H₂O+e⁻,  (6)

[0052] where direction from left to right is charging, from right toleft is discharging.

[0053] In this reaction (6) hydroxide-ion and electrolyte waterparticipate, i.e. the reaction proceeds under conditions when nickelhydroxide is in contact with electrolyte It may appear that if Ni(OH)₂molecules are arranged inside the metal phase of the active element thenthe proceeding of reaction (6) is impossible. However, as experienceshows and as the explanatory examples given below indicate, it is notthe case, reaction (6) proceeds, and with rather high rate, even underthese conditions. In order to explaine this it is practical to re-writereaction (6) in a little different form taking into account possiblepresence of absorbed hydrogen H_(ab) in the matrix of the activeelement:

[0054] where direction from left to right is charging, from right toleft is discharging.

[0055] Combination of reactions (7) and (8) gives the reaction ofinternal oxidation of nickel which is related to absorption of oxygenand to decrease of absorbed hydrogen content in nickel. Reaction (8)proceeds on the surface of active element in contact with theelectrolyte, reaction (7)—in the volume of the active element, so thatmechanism of reactions (7)-(8) implies diffusion of absorbed hydrogen inthe active element.

[0056] Presence of a great amount of absorbed hydrogen in electrolyticalloys (deposits) of metals and its rather high diffusion rate have beenestablished long ago (O. P. Smith. Hydrogen in metals. Chicago, USA,1948, 367 p). It has been noted that the amount of absorbed hydrogen inelectrolytic deposits of such metals as tin, copper, nickel, cobalt,iron, manganese, chromium, zinc, and in the electrolytic alloys on thebasis of these metals is several orders larger than the equilibriumsolubility of hydrogen in the same metals and alloys obtained in ametallurgical process. The reasons for this phenomenon are beingdiscussed, beginning with the very early works and up to the presenttime, and up to now they have remained unclear. Nevertheless, theavailability of hydrogen able to be absorbed by electrolyticallydeposited metals and alloys, is beyond question and creates theoreticalprerequisite for practical implementation of this phenomenon not onlyfor positive electrodes (to provide proceeding of reactions of (7)-(8)type) but also for negative electrodes where reactions of hydrogenabsorption/desorption can proceed:

H₂O+e⁻⇄H_(ab)+OH⁻,  (9)

[0057] where direction from left to right is charging, from right toleft is discharging.

[0058] For example, in cited above book by O. P. Smith it has beenestablished that electrolytic alloys (deposits) of iron can absorb up to3% at. of hydrogen, nickel—up to 0.4% at, cobalt—up to 1.6% at. It canbe easily calculated that a 30 □m thick galvanic deposit (mass 25mg/cm²) containing 5% at. of hydrogen can accumulate a charge accordingto reaction (9) of about 2,5 C/cm² which exceeds by several times thespecific charge of e.g. electrode of carbon materials operating bydouble-layer mechanism (see RU, Cl, 2145132).

[0059] Observations made by L. V. Volkov et al. (L. V. Volkov, S. I.Gusev, V. N. Andrushchenko. Non-ferrous metals, 1981, No. 2, pp. 28-29)that there exists a strong correlation between content of absorbedoxygen and absorbed hydrogen in electrolytic nickel, atomic ratiobetween hydrogen and oxygen being between one and two, are offundamental importance as theoretical evidence of feasibility inrealizing the claimed concepts. In the article there is no explanationof this fact but one can suppose that (M-OH)-groups being present inelectrolytic deposit can somehow coordinate nearby them one more atom ofhydrogen. Regardless of mechanism of this phenomenon, it is of greatimportance for practical realization of the claimed concepts: the more(M-OH)-groups the electrolytic alloy (deposit) contains the morehydrogen it is able to absorb, consequently the more charge can beaccumulated both by reactions (7)-(8) and (9). It means that the moreabsorbed oxygen the electrolytic deposits, e.g. nickel or nickel alloys,contain, the more they contain absorbed hydrogen as well, and thatmeans—the better they would operate both as positive and negativeelectrodes.

[0060] The explanatory examples given below corroborate thisproposition, not at all self-evident, which is a consequence of theknown scientific facts above.

[0061] It is worth noting that many works on studying the hydrogenabsorption in electrolytically deposited metals are directed towardsstudying problems for overcoming the harmful effect of “hydrogenization”causing “embrittlement” and peeling off the galvanic deposits andappearance of unwanted entrapped gases in electrolytically obtainednickel, etc. The works known to public don't contain any information orrecommendations on the employment of the “hydrogenization” phenomenon inthe electrodes of electrochemical storage devices nor any other usefulemployment of the phenomenon.

[0062] Considering the phenomenon of excessive hydrogen and oxygenabsorption not as a deleterious phenomenon but as a useful one it ispossible to deliberately increase the content of hydrogen and oxygen byoptimizing the electric deposition process, e.g. enhancing the currentdensity during electric deposition (O. P. Smith. Hydrogen in Metals.Chicago, USA, 1948, 367 p.). It would be appropriate to use for positiveelectrode electrolytic nickel or electrolytic alloy on the basis ofnickel, in which atomic fraction of absorbed oxygen x is within thelimits of 0.01≦x≦0.4, preferably within the limits of 0.05≦x≦0.4, andfor negative electrode electrolytic nickel, iron, cobalt or electrolyticalloys on the basis of these metals, in which atomic fraction ofabsorbed hydrogen y is within the limits of 0.01≦y≦0.4, preferablywithin the limits of 0.05≦y≦0.4.

[0063] The choice of material composition for positive and negativeelectrodes is dictated by the following considerations.

[0064] In the region of potentials where positive electrode operatesonly a small group of metals (nickel, silver, noble metals) is stable inalkaline aqueous solutions. Cobalt and iron are stable to a lesserextent. Therefore, from economical point of view the most preferablematerial for active element of a positive electrode is electrolyticnickel or electrolytic alloys on its basis containing rather largenumber of (M-OH)-groups in the structure but not too large, in whichcase electrolytic deposits could be too brittle and with lowconductivity.

[0065] In the region of potentials where negative electrode operates thefollowing metals and alloys on their basis are stable in alkalineaqueous solutions: iron, nickel, cobalt, cadmium, zirconium. Bismuth andtitanium are stable at a lesser extent. Cadmium is to be excluded onecological grounds and zirconium—on economical grounds. Therefore,preferable materials for negative electrode are electrolytic iron,nickel, cobalt and electrolytic alloys on the basis of one of thesemetals, containing large enough amount of absorbed hydrogen however notso large as to obtain too brittle electrolytic deposits having too lowconductivity.

[0066] The said limits of absorbed oxygen and hydrogen content in theactive element material of positive and negative electrode respectivelyhave been determined on the basis of experimental results. Inparticular, the experiments have shown that at absorbed oxygen andhydrogen content beyond 40% at. the electrolytic deposits lose theirplasticity, become brittle and can crumble and peel off under cyclicloads. At oxygen content in positive electrode and hydrogen content innegative electrode below 5% at. specific charges of charging/dischargingof the electrodes are too small and such electrodes cannot compete withcommercially known electrodes.

[0067] It should be particularly emphasized that the offered electrodesof electrolytic alloys (the first and the second embodiments of theclaimed invention) can be used in electrochemical energy storage deviceseither together (the third embodiment of the invention) or in differentcombinations with known electrodes (the fourth and fifth embodiments ofthe invention). Thus, the negative electrode according to the secondembodiment in accordance with the fourth embodiment of the invention canbe used with a known positive electrode, e.g. with positive electrode ofprototype, and the positive electrode according to the first embodimentin accordance with the fifth embodiment of the invention can be usedwith a known negative electrode, e.g. made of a carbon material.

[0068] To the applicants' knowledge the works known to the public don'tcontain any information about influence of characteristic features ofthe claimed concept on the reached technical result. The saidcircumstance allows to draw a conclusion that the claimed technicalconcepts conform the criterion “inventive standard” (IS).

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Hereinafter the invention will be elucidated with detaileddescription of 15 examples of realization of the same with reference tothe accompanying drawings, in which:

[0070] In FIG. 1 there is presented a schematic diagram of adouble-electrode electrochemical energy storage device in the variantwith the claimed electrodes on the backing.

[0071] In FIG. 2 there is presented a cyclic voltammagram of the claimedelectrode according to the eighth example in the region of potentialsfor operation of negative electrode.

[0072] In FIG. 3 there is presented a cyclic voltammagram of the claimedelectrode according to the eighth example in the region of potentialsfor operation of positive electrode.

[0073] In FIG. 4 there is presented a cyclic voltammagram of the claimedelectrode according to the ninth example in the region of potentials foroperation of positive electrode.

[0074] In FIG. 5 there are presented discharge curves for a model of theclaimed electrochemical energy storage device with electrodes producedin accordance with the sixth and tenth examples.

[0075] In FIG. 6 there is presented a dependence of discharging chargeon number of charge/discharge cycles for a model of the claimedelectrochemical energy storage device with electrodes produced inaccordance with the sixth and tenth examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] The claimed electrochemical energy storage device of highspecific power according to the third embodiment of the claimedinvention in the realization variant being discussed (FIG. 1) comprisesnegative electrode 1 and positive electrode 2 manufactured according tothe first and second embodiments of the claimed invention.

[0077] Electrodes 1 and 2 are submersed in aqueous alkaline electrolyte(not shown in FIG. 1). Electrodes 1 and 2 are set apart by a separator3—a layer of ion-conductive but non electron-conductive material. Asseparator e.g. a layer of porous polymer impregnated with electrolytecan be used.

[0078] Negative 1 and positive 2 electrodes comprise active elements 4and 5 interacting with electrolyte in the process of redox reaction ofcharging/discharging. Active elements 4 and 5 are made of a conductiveelectrolytic alloy (deposit) which simultaneously functions ascurrent-carrying collector and as active material taking part inprocesses of charging/discharging redox reactions in electrodes 1 and 2respectively.

[0079] Active element 4 of negative electrode 1 is made of anelectron-conductive electrolytic alloy (deposit) of compositionM_((l-x-y))O_(x)H_(y), where M is metal of the following group: iron,nickel, cobalt, or an alloy on the basis of one of the metals of thisgroup with content of the main component at least 40% mass., x is atomicfraction of absorbed oxygen in the electrolytic alloy being withinlimits of 0.01≦x≦0.4, y is atomic fraction of absorbed hydrogen in theelectrolytic alloy being within limits of 0.01≦x≦0.4, preferably withinlimits of 0.05≦y≦0.4. The said limits of absorbed hydrogen content arecaused by the fact that at lesser hydrogen content specific charge ofcharging/discharging is too small and does not provide competitivenessof the negative electrode while at larger content the deposit becomesbrittle and its cycling stability falls.

[0080] Active element 5 of positive electrode 2 is made of anelectron-conductive electrolytic alloy (deposit) of compositionM_((l-x-y))O_(x)H_(y). where M is nickel or a nickel-based alloy withcontent of the main component at least 40% mass., x is atomic fractionof absorbed oxygen in the electrolytic alloy being within limits of0.01≦x≦0.4, preferably within the limits of 0.05≦x≦0.4, y is atomicfraction of absorbed hydrogen in the electrolytic alloy being withinlimits of 0.01≦x≦0.4. The said limits of absorbed oxygen content arecaused by the fact that at lesser oxygen content specific charge ofcharging/discharging is too small and does not provide competitivenessof the negative electrode while at larger content the deposit becomesbrittle and its cycling stability falls.

[0081] The said electrolytic alloys (deposits) are obtained by mutualelectrochemical cathode co-deposition of metals belonging to the saidgroups M, their oxides and/or hydroxides.

[0082] In the discussed example of realization the active elements 4 and5 of electrodes 1 and 2 are formed as electrolytic deposits onrespective conductive backings 6 and 7, through which in the presentdesign current supply to the active elements 4 and 5 is carried out. Inorder to realize their functions the backings 6 and 7 are made of amaterial chemically and electrochemically stable in the workingelectrolyte of the electrochemical energy storage device.

[0083] In other variants of realization (not shown in FIG. 1) the activeelements 4 and 5 of the electrodes 1 and 2 can be formed as independentconstructive elements as electrolytic deposits mechanically, chemicallyor electrochemically separated from respective conductive backings onwhich they have been deposited. In this case the active elements 4 and 5are used without backings and current supply in electrodes 1, 2 iscarried out directly to the active elements 4 and 5.

[0084] Electrochemical energy storage device according to the fourthembodiment of the claimed invention differs from the above consideredelectrochemical energy storage device according to the third embodimentof the claimed invention by that, that as positive electrode any knownand used for such purposes positive electrode is employed provided thatit is stable in aqueous alkaline electrolyte, e.g. positive electrodemade of carbon, nickel, cobalt or silver. In particular, the positiveelectrode described in prototype can be used as a positive electrode.

[0085] Electrochemical energy storage device according to the fifthembodiment of the claimed invention differs from the electrochemicalenergy storage device according to the third embodiment of the claimedinvention by that, that as negative electrode any known and used forsuch purposes negative electrode is employed provided that it is stablein aqueous alkaline electrolyte, e.g. a negative electrode made ofcarbon, nickel, cobalt or iron. In particular, carbon electrode used inhybrid, capacitors can be employed as negative electrode.

[0086] The electrochemical energy storage devices made in the wayconsidered above (according to the third, fourth and fifth embodiments)are characterized with improved specific characteristics and increasedservice life which is defined by permissible number of charge/dischargecycles. Improvement of properties is caused with that a new principle ofmutual arrangement of main phases participating in current producingreactions is realized in the electrodes which differs from the prototypeand consists in that active material (oxides and/or hydroxides) isarranged within a metal collector (being a part of its crystalstructure) and forms with it a unified phase—the phase of “activeelement”.

[0087] The examples of specific executions of electrodes andelectrochemical energy storage devices given below confirm feasibilityand industrial applicability of the claimed invention and attainment ofthe required result.

[0088] The elucidatory examples 1 to 7 relate to negative electrodesaccording to the second embodiment of the claimed invention. Conditionsof production (electrolyte composition, electrolysis conditions) andproperties of negative electrodes according to examples 1 to 7 arepresented in Table 1 in the end of the description. Conditions andmethods of measurement are similar for all the elucidatory examples 1-7and presented in example 1.

EXAMPLE 1

[0089] The negative electrode is obtained by electrochemical deposition(electrodeposition) of nickel on the backing made of rolled nickel foil25 μm thick under conditions given in Table 1. The composition of theobtained electrolytic alloy (deposit)—Ni_(0,67)O_(0,13)H_(0,2)—wasdefined by gas analysis of the deposit. Specific charge of the electrodewas defined by discharge curves at galvanostatic discharge of theelectrode in 30% KOH solution. Prior to discharge the electrode was heldat the potential of minus 1,0 V against mercury oxide referenceelectrode during 5 minutes. Discharging with current density of 0,1A/cm² continued until attainment of potential of minus 0,6 V. Thedischarge curve was plotted by a high speed recorder. The specificcharge was defined by multiplying the time of discharge in seconds bythe current density 0,1 A/cm². At deposit thickness of 25 μm (mass being20 mg/cm²) specific charge of the electrode is 2,3 C/cm² or 115 C/g.This value is five times higher than corresponding value for negativeelectrode in the prototype.

EXAMPLE 2

[0090] The negative electrode is obtained as in example 1 but in adifferent electrolyte and under different conditions of electrochemicaldeposition (see Table 1). Composition of the obtained electrolyticsediment is Ni_(0,63)O_(0,15)H_(0,22), mass is 17 mg/cm², specificcharge is 165 C/g which is higher than in example 1.

EXAMPLE 3

[0091] The negative electrode is obtained (see Table 1) byelectrodeposition of nickel-cobalt alloy on polished titanium backingwith following mechanical separation of the deposit from the backing(galvanoplastic method). Cobalt chloride was added to the electrolyte.Composition of the obtained electrolytic deposit isNi_(0,52)Co_(0,10)O_(0,015)H_(0,23), mass is 17 mg/cm², specific chargeis 170 C/cm². The deposit separated from the backing is plastic and canbe used as an electrode without any additional collector.

EXAMPLE 4

[0092] The negative electrode is obtained (see Table 1) byelectrodeposition of nickel-iron alloy on polished titanium backing withfollowing mechanical separation of the deposit from the backing. Ferrousiron sulphate was added to the electrolyte. Composition of the obtainedelectrolytic deposit is Ni_(0,53)Fe_(0,13)O_(0,14)H_(0,20), mass is 24mg/cm², specific charge is 133 C/g. The electrolytic deposit separatedfrom the backing is strong, plastic and can be used as an electrodewithout any additional collector.

EXAMPLE 5

[0093] The negative electrode is obtained (see Table 1) byelectrodeposition of cobalt-nickel alloy on polished titanium backingwith following mechanical separation of the deposit from the backing.Composition of the obtained electrolytic deposit isCo_(0,54)Ni_(0,15)O_(0,13)H_(0,18), mass is 20 mg/cm², specific chargeis 150 C/g. The electrolytic deposit separated from the backing isstrong, plastic and can be used for forming of a cylindrical electrode,e.g. by winding on a cylindrical mandrel Ø5 mm.

EXAMPLE 6

[0094] The negative electrode is obtained (see Table 1) byelectrodeposition of nickel-iron alloy on polished titanium backing withfollowing mechanical separation of the deposit from the backing.Composition of the obtained electrolytic deposit is from the backing isstrong, plastic and can be used as an electrode without any additionalcollector.

EXAMPLE 7

[0095] The negative electrode is obtained (see Table I) byelectrodeposition of nickel-palladium alloy on a backing of rollednickel foil 25 μm thick. Composition of the obtained electrolyticdeposit is Ni_(0,60)Pd_(0,03)O_(0,16)H_(0,21), mass is 17 mg/cm²,specific charge is 176 C/g.

[0096] The presented examples 1 to 7 prove possibility of practicalrealization of the second embodiment of the claimed invention in respectto negative electrodes. In these examples the content of absorbedhydrogen in electrolytic alloys (deposits) varied between 18% and 25%at. Additional experiments related to determination of limits ofpermissible content of absorbed hydrogen in electrolytic alloys(deposits) used in negative electrodes have shown that at increase inabsorbed hydrogen content up to 40% at. the charge released whiledischarging has increased as well as the specific energy however theelectrolytic alloy (deposit) has become brittle and could only be usedon a backing, e.g. on nickel foil or mesh. For electrodes obtained bygalvanoplastics method in which current supply is carried out directlyto the active element (electrolytic deposit) the hydrogen content mustbe lower, e.g. similar to hydrogen content in the above discussedexamples 1 to 7. The lower limit for absorbed hydrogen content inelectrolytic deposit for a negative electrode must not be below 1% at.because at this point the specific charge falls down to values that makethe electrode useless for practical applications.

[0097] The following explanatory examples 8 to 10 relate to positiveelectrodes according to the first embodiment of the claimed invention.Conditions of fabrication (electrolyte composition, electrolysisconditions) and properties of positive electrodes according to theseexamples are presented in Table 2 in the end of the description.Conditions and methods of measurement according to these examples aresimilar and presented in example 8.

EXAMPLE 8

[0098] The positive electrode is obtained by electrochemical deposition(electrodeposition) of nickel on a backing of nickel foil 25 μm thickunder conditions given in Table 2. Composition of obtained electrolyticalloy (deposit) is Ni_(0,65)O_(0,18)H_(0,17), mass is 25 mg/cm²,specific charge is 88 C/g.

[0099] Specific charge was defined by the galvanostatic dischargingcurve from potential +0.52 V down to +0.1 V by current density 0.1 A/cm²in 30% aqueous KOH solution. Before discharge the electrode was held atpotential +0.52 V during 5 minutes.

[0100] In FIG. 2 there is presented a cyclic voltammagram of theelectrode according to the eighth example in 30 % KOH solution. Theelectrode area is 4 cm², reference electrode is a mercury oxideelectrode, sweep rate is 10 mV/s. At the charging potential minus 1.0 Vthe holding time was 50 seconds.

[0101] In FIG. 3 there is presented a cyclic voltammagram of the sameelectrode but in the potential region of positive electrode operation.Sweep rate is 10 mV/s. At the charging potential +0.52 V the holdingtime was 50 seconds.

EXAMPLE 9

[0102] The positive electrode is obtained (see Table 2) byelectrodeposition of a nickel-cobalt alloy on a backing of nickel foil25 μm thick. Composition of the obtained electrolytic deposit isNi_(0,55)Co_(0,1)O_(0,19)H_(0,16), mass is 25 mg/cm², specific charge is96 C/g.

[0103] In FIG. 4 there is presented a cyclic voltammagram of theelectrode according to the ninth example in the potential region ofpositive electrode operation. The electrode area is 4 cm², sweep rate is10 mV/s. At the charging potential +0.55 V the holding time was 50seconds. Comparison of voltammagrams in FIG. 3 and in FIG. 4 shows thatby alloying it is possible to increase the specific charge of thepositive electrode.

EXAMPLE 10

[0104] The positive electrode is obtained (see Table 2) byelectrodeposition of a nickel-zinc-cobalt alloy on a polished titaniumbacking with following mechanical separation of the deposit from thebacking (galvanoplastic method). Composition of the obtainedelectrolytic deposit is Ni_(0,52)Co_(0,09)Zn_(0,02),O_(0,20)H_(0,17),mass is 36 mg/cm², specific charge is 119 C/cm².

[0105] The presented examples 8 to 10 prove feasibility of practicalrealization of the first embodiment of the claimed invention in respectto positive electrodes. In these examples content of absorbed oxygen inelectrolytic alloys (deposits) varied from 18% to 20% at. Additionalexperiments related to determining permissible limits of absorbed oxygencontent in electrolytic alloys (deposits) used in positive electrodeshave indicated that at increase of absorbed oxygen content up to 40% at.the charge released at discharging increased as well as the specificenergy however the electrolytic alloy (deposit) lost its strength andplasticity, its conductivity decreased. At absorbed oxygen content below1% at. the specific charge falls down to values that make the electrodeuseless for practical applications.

[0106] It is of great importance to emphasize the following fact, whichis readily apparent from analyzing cyclic voltammagrams of the electrodeaccording to the eighth example (see FIG. 2 and 3). The cyclicvoltammagrams FIG. 2 and 3 were measured on one and the same electrode,first in the region of cathode potentials, then in the region of anodepotentials. These voltammagrams prove that one and the same electrodemade according to the first or second embodiment of the claimedinvention can operate both as negative and as positive electrode. Thissupports validity of earlier presented explanations of possiblemechanism of charging-discharging processes for positive and negativeelectrodes in accordance with reactions (7)-(8) and (9). It can also bestated that the established fact that one and the same electrode canoperate both as negative and positive electrode is the best proof infavor of the hypothesis that absorbed hydrogen and oxygen dwell inelectrolytic deposits in the form of M-OH groups, possibly in veryfine-dispersed phase. At any rate, SEM photographs of deposits atmagnification ×30,000 did not permit to distinguish any fine structureof the deposit. It should be noticed as well that though negativeelectrodes (Table 1) can operate as positive ones, it is still better tochose most suitable deposition conditions specially for obtainingpositive electrodes (Table 2).

[0107] Two waves of discharging current are readily seen in thevoltammagram FIG. 2. They indicate existence of two forms of absorbedhydrogen in the active material of the electrode. One form of weakerbonded hydrogen is absorbed at potentials from minus 0.9 V to minus 1.0V and desorbed at potentials from minus 1.0 V to minus 0.75 V, thesecond form, more strongly bonded, is absorbed at potentials from minus0.8 V to minus 0.9 V and is desorbed at potentials from(minus 0.75 V tominus 0.65 V. Such a behavior correlates with conclusions made half acentury ago (Yu. V. Baymakov, L. M. Yevlannikov. J. Ph. Ch., 1951, v.25,issue 4, pp. 483-494) about existence of two forms of absorbed hydrogenbeing released at vacuum annealing, one form at a temperature of450-500° C., the other at temperatures beyond 800° C.

[0108] The proposed negative and positive electrodes presented inexamples 1 to 7 (see Table 1) and in examples 8 to 10 (see Table 2) canbe used in the following three variants of electrochemical energystorage devices: with both proposed electrodes—positive and negativeones which corresponds to the third embodiment of the claimed invention;with proposed negative electrode and a known positive electrode, e.g. anelectrode of the prototype, which corresponds to the fourth embodimentof the claimed invention; with proposed positive electrode and a knownnegative electrode, e.g. a carbon one, which corresponds to the fifthembodiment of the claimed invention.

[0109] Models of electrochemical energy storage devices related to thefirst variant of execution are presented in examples 11-12, the secondvariant is presented in example 13, the third one—in example 14. Example15 is a reference example, it relates to an electrochemical energystorage device in which a known negative electrode of carbon materialand a known positive electrode made in accordance with the prototype areused.

[0110] The properties of electrochemical energy storage devicesaccording to examples 11-15 are presented in Table 3 given in the end ofthe description. Measurement conditions in examples 11-15 are similarand presented in example 11.

EXAMPLE 11

[0111] The model of electrochemical energy storage device according tothe third embodiment of the claimed invention is assembled of thenegative electrode described in example 6 and the positive electrodedescribed in example 10 divided by separator of 0.05 mm thickpolypropylene paper wetted with electrolyte—30% KOH solution. The modelof electrochemical energy storage device was charged by current of 0.4 Aup to voltage of 1.5 V, then held during 5 minutes at constant voltageof 1.5 V. Discharge curves were recorded at three constant values of thecurrent 0.04 A, 0.4 A and 1.6 A at temperature 20° C. Change of voltagein time was plotted with a high-speed recorder. Discharging continueduntil attainment of voltage 0.7 V. Charge of discharging was defined bymultiplying the discharge current by the discharge time while averagevoltage was defined by numerical integration of the “voltage-time”curve. Mass of the model was determined by using of scale.

[0112] Calculation of specific energy and specific power was carried outby formulae (4) and (5), results of the calculations are presented inTable 3.

[0113] In FIG. 5 there are presented discharge curves of the presentmodel of electrochemical energy storage device. These curves have ashape intermediate between discharge curves of accumulators and those ofcapacitors. At small values of discharge current they are more close todischarge curves of an accumulator, at larger values—more close todischarge curves of a capacitor.

[0114] Durability test of the present model of electrochemical energystorage device under cyclic loads is illustrated by the curve in FIG. 6which represents how discharging charge depends on number ofcharge/discharge cycles. The test has shown that service life exceeds43,000 cycles during which no change in discharging charge has beenregistered—such was the number of cycles during the tests up to themoment of applying the patent.

[0115] Charging while cycling was carried out with a current of 0.4 Auntil attainment of voltage 1.5 V, then the voltage was held constantduring one minute. Discharging was carried out with a current of 0.4 Auntil attainment of voltage 1.1 V (50% of total charge), then the cyclewas repeated. Charge of discharging was determined by multiplyingcurrent (0,4 A) by discharge time in seconds. Temperature range whilecycling was 18÷20° C.

[0116] Increase in durability of electrochemical energy storage devicewith the proposed electrodes under cyclic loading as compared to thedurability of prototype is quite explainable. The active elements of theclaimed electrodes present compact electrolytic deposits instead ofhighly porous layers with large true surface so that all the reactionsof chemical and electrochemical dissolution proceed here withincomparably lower rate. At the same time, reactions (7), (8), (9)proceed rapidly enough owing to high hydrogen penetrability ofiron-group metals, especially of electrolytic deposits of these metals.

EXAMPLE 12

[0117] The model of electrochemical energy storage device according tothe third embodiment of the claimed invention is made in the same manneras in example 11 but with other negative and positive electrodesaccording to examples 3 and 9 respectively (see Table 3). Use of theseelectrodes results in some dissimilarities in characteristics ofspecific energy and power of this electrochemical energy storage deviceas compared with the electrochemical energy storage device in example 11(see table 3).

EXAMPLE 13

[0118] The model of electrochemical energy storage device according tothe fourth embodiment of the claimed invention is assembled withnegative electrode made according to example 6 and with positiveelectrode made as in the prototype. In comparison with the prototype themodel of this electrochemical energy storage device has essentialadvantages in specific energy and power, moreover, it does not containecologically harmful cadmium. However, the model of this electrochemicalstorage device (see Table 3) is inferior to the model of electrochemicalenergy storage device described in example 11 where the same negativeelectrode is used but the positive electrode is made in accordance withthe claimed invention. The device in example 11 also has a smaller massdue to the combination of current collector and active materialfunctions in the active element.

EXAMPLE 14

[0119] The model of electrochemical energy storage device according tothe fifth embodiment of the claimed invention is assembled with negativeelectrode of 0.35 mm thick carbon fabric and positive electrodeaccording to example 10. A 4-6 μm thick nickel layer was deposited onone side of carbon fabric by method of cyclotron spraying, after thatthe carbon fabric was spot welded at nine points to 25 μm thick nickelfoil used as collector. The rest of manufacturing conditions andprocedure of measurements were as in example 11. As it is seen fromTable 3, the model of such electrochemical energy storage device issubstantially inferior to the models of electrochemical energy storagedevices presented in examples 11 and 12 where both electrodes are madeaccording to the claimed proposal, as well as to the model ofelectrochemical energy storage device presented in example 13 where thenegative electrode is made according to the claimed proposal and thepositive one is made as in the prototype. By specific power at highcurrent densities the model of such an electrochemical energy storagedevice as in example 14 is close to the model of electrochemical energystorage device as per example 13 but is inferior to the models ofelectrochemical energy storage devices as per examples 11 and 12 (seeTable 3).

EXAMPLE 15

[0120] The model of electrochemical energy storage device is assembledwith both electrodes of known types. As positive electrode an electrodewas used made as in example 13 according to the prototype while thenegative electrode was made on the basis of carbon fabric as in example14. The rest of manufacturing and measurement conditions were as inexample 11. As it is seen from the data given in Table 3 the model ofthis electrochemical energy storage device is inferior to all theprevious examples 11 to 14 both by specific energy and by specificpower.

INDUSTRIAL APPLICABILITY

[0121] As can be seen from all the above all embodiments of the claimedinvention it is scientific feasible, industrial performable and solvethe set task, namely it increases the service life (increase in numberof recharge cycles) without decreasing (and even with increasing) thespecific power and energy, furthermore the ecological harmful cadmium isexcluded from the structural materials of the device.

[0122] The possibility of industrial application of the claimedtechnical concepts is beyond any doubt because they can be realizedusing conventional materials and well-known industrial equipment, sothat a conclusion can be drawn that the claimed invention conform thecriterion “Industrial applicability” (IA).

[0123] The claimed embodiments of the invention present a substantialpractical interest, opening up a new, never used before, direction indesigning electrochemical energy storage devices of high specific powerbased on the employment of active elements in electrodes made out ofelectron-conductive electrolytic alloys (deposits) with excessivecontent of absorbed oxygen and hydrogen providing proceeding ofcharge-discharge redox reactions, the electrolytic alloy (deposit)functioning at the same time as current-carrying collector and as activematerial.

[0124] The prospects of this direction are stipulated by thepotentialities of a substantial enhancement of the service life ofelectrochemical energy storage devices of high specific power andenergy, by simplicity and low cost of their realization and by absenceof ecological harmful materials in the device. TABLE 1 Fabricationconditions of negative electrodes and their properties ElectrolyteCurrent Electrolysis Coating Specific Example composi-tion, Temperaturedensity, duration, thickness, charge No. g/l ° C. A/cm² min. μm C/cm²Note 1 NiSO₄-150 70 12 10 25 2,3 Backing - NiCl₂-50 nickel foil H₃BO₃-1025 μm 2 NiSO₄-50 50 10 10 20 2,8 Backing - NiCl₂-150 nickel foilH₃BO₃-10 25 μm 3 NiSO₄-150 50 10 10 20 2,9 Galvano- NiCl₂-10 plasticfrom CoCl₂-10 titanium H₃BO₃-10 backing 4 NiSO₄-100 70 15 10 30 3,2Galvano- NiCl₂-10 plastic from FeSO₄-30 titanium H₃BO₃-10 backing 5NiSO₄-50 50 12 10 25 3,0 Galvano- CoCl₂-150 plastic from H₃BO₃-10titanium backing 6 NiSO₄-50 70 20 10 40 4,0 Galvano- Fe Cl₂-100 plasticfrom H₃BO₃-10 titanium backing 7 NiSO₄-50 50 10 10 20 3,0 Nickel foilNiCl₂-150 backing PdCl₂-2 25 μm H₃BO₃-10

[0125] TABLE 2 Fabrication conditions of positive electrodes and theirproperties Electrolyte Current Electrolysis Coating Specific Examplecomposition, Temperature density, duration, thickness, charge No. g/l °C. A/cm² min. μm C/cm² Note 8 NiSO₄-100 40 10 15 30 2,2 Nickel NiCl₂-30foil H₃BO₃-10 backing 25 μm 9 NiSO₄-100 50 15 10 30 2,4 Nickel- CoCl₂-10foil KCl-20 backing H₃BO₃-10 25 μm 10  NiSO₄-100 50 15 15 45 4,3Galvano- CoCl₂-10 plastic ZnCl₂-20 from H₃BO₃-10 titanium backing

[0126] TABLE 3 Properties of energy storage models Example No.$\frac{\begin{matrix}{Negative} \\{electrode}\end{matrix}}{\begin{matrix}{Positive} \\{electrode}\end{matrix}}\quad$

Model mass, g Current, A Discharging charge, C Average dischargingvoltage, V Specific energy, J/g Average specific power, W/g 11$\frac{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{{example}\quad 6}\end{matrix}}{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{{example}\quad 10}\end{matrix}}$

0.32 0.04 0.4 1.6 16 12  4.4 1.2 1.1 0.85 60 41 11.7 0.15 1.37 4.25 12$\frac{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{{example}\quad 3}\end{matrix}}{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{{example}\quad 9}\end{matrix}}$

0.25 0.04 0.4 1.6  9.6  7.2  2.8 1.2 1.1 0.85 46 31.7  9.5 0.19 1.76 5.413 $\frac{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{{example}\quad 6}\end{matrix}}{\begin{matrix}{{electrode}\quad {as}\quad {per}} \\{prototype}\end{matrix}}$

0.39 0.04 0.4 1.6 16 12.8  5.2 1.2 1.1 0.85 49.2 36.1 11.3 0.12 1.133.50 14 $\frac{\begin{matrix}{{{Carbon}\quad {fabric}}\quad} \\{0.35\quad {mm}}\end{matrix}}{\begin{matrix}{{Electrode}\quad {as}\quad {per}} \\{{example}\quad 10}\end{matrix}}$

0.43 0.04 0.4 1.6  8.4  6.0  2.8 1.05 1.0 0.9 20.5 14  5.9 0.10 0.933.35 15 $\frac{\begin{matrix}{{{Carbon}\quad {fabric}}\quad} \\{0.35\quad {mm}}\end{matrix}}{\begin{matrix}{{Electrode}\quad {as}\quad {per}} \\{prototype}\end{matrix}}$

0.50 0.04 0.4 1.6  8.4  6.4  4.0 1.05 1.0 0.9 17.6 12.8  7.2 0.084 0.802.90

1. A positive electrode for an electrochemical energy storage device ofhigh specific power comprising active element interacting with aqueousalkaline electrolyte of the electrochemical energy storage device in theprocess of redox charge-discharge reactions characterized in that theactive element is made of electron-conductive electrolytic alloy havingthe composition M_((l-x-y))O_(x)H_(y), where M is nickel or nickel-basedalloy, x is the atomic fraction of absorbed oxygen in the electrolyticalloy being within the limits of 0.01 to 0.4, y is the atomic fractionof absorbed hydrogen in the electrolytic alloy being within the limitsof 0.01 to 0.4, whereby the said electrolytic alloy simultaneouslyfulfils the functions of current-carrying collector and of activematerial participating in the processes of redox charge-dischargereactions.
 2. The electrode according to claim I characterized in thatthe atomic fraction x of absorbed oxygen in the electrolytic alloy ispreferably within the limits of 0.05 to 0.4.
 3. The electrode accordingto claim 1 characterized in that the electrolytic alloy is obtained byway of simultaneous electrochemical cathode co-deposition of a metalbelonging to the above mentioned M metal group and its oxides and/orhydroxides.
 4. The electrode according to claim 1 characterized in thatthe current supply is effected directly to the active element which isstructurally designed as an electrolytic deposit being mechanically,chemically or electrochemically separated from an electro-conductivebacking on which it had been deposited.
 5. The electrode according toclaim 1 characterized in that the current supply is effected to theactive element via a backing, the active element being structurallydesigned as an electrolytic deposit on one or both sides of theelectro-conductive backing made of a material chemically andelectrochemically stable in the electrolyte of the electrochemicalenergy storage device.
 6. A negative electrode for an electrochemicalenergy storage device of high specific power comprising active elementinteracting with aqueous alkaline electrolyte of the electrochemicalenergy storage device in the process of redox charge-discharge reactionscharacterized in that the active element is made of electron-conductiveelectrolytic alloy having-the composition M_((l-x-y))O_(x)H_(y), where Mis a metal of the group: iron, nickel, cobalt, or an alloy on the basisof one of the metals of this group, x is the atomic fraction of absorbedoxygen in the electrolytic alloy being within the limits of 0.01 to 0.4,y is the atomic fraction of absorbed hydrogen in the electrolytic alloybeing within the limits of 0.01 to 0.4, whereby the said electrolyticalloy simultaneously fulfils the functions of current-carrying collectorand of active material participating in the processes of redoxcharge-discharge reactions.
 7. The electrode according to claim 6characterized in that the atomic fraction y of absorbed hydrogen in theelectrolytic alloy is preferably within the limits of 0.05 to 0.4. 8.The electrode according to claim 6 characterized in that theelectrolytic alloy is obtained by way of simultaneous electrochemicalcathode co-deposition of a metal belonging to the above mentioned Mmetal group and its oxides and/or hydroxides.
 9. The electrode accordingto claim 6 characterized in that the current supply is effected directlyto the active element which is structurally designed as an electrolyticdeposit being mechanically, chemically or electrochemically separatedfrom an electro-conductive backing on which it had been deposited. 10.The electrode according to claim 6 characterized in that the currentsupply is effected to the active element via a backing, the activeelement being structurally designed as an electrolytic deposit on one orboth sides of the electro-conductive backing made of a materialchemically and electrochemically stable in the electrolyte of theelectrochemical energy storage device.
 11. An electrochemical energystorage device of high specific power containing at least one negativeand one positive electrodes submerged in aqueous alkaline electrolyteand separated with a layer of ion-conductive but non electron-conductivematerial, whereby each electrode contains an active element interactingwith the electrolyte in the process of charge-discharge redox reactionscharacterized in that the active element of each electrode is made outof an electron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M for positive electrode is nickel or analloy on the basis of nickel, M for negative electrode is a metal out ofthe following metal group: iron, nickel, cobalt or an alloy on the basisof one of the metals of this group, x is an atomic fraction of absorbedoxygen in the electrolytic alloy which is within the limits of 0.01 to0.4, y is an atomic fraction of absorbed hydrogen in the electrolyticalloy which is within the limits of 0.01 to 0.4, whereby the abovementioned electrolytic alloy simultaneously fulfills the functions ofcurrent-carrying collector and of active material participating in theprocesses of redox charge-discharge reactions of each of the electrodes.12. The electrochemical energy storage device according to claim 11characterized in that for the positive electrode the atomic fraction xof absorbed oxygen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4 while for the negative electrode atomic fraction yof absorbed hydrogen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4.
 13. An electrochemical energy storage device ofhigh specific power containing at least one negative and one positiveelectrodes submerged in aqueous alkaline electrolyte and separated witha layer of ion-conductive but non electron-conductive material, wherebyeach electrode contains an active element interacting with theelectrolyte in the process of charge-discharge redox reactionscharacterized in that the active element of the negative electrode ismade of an electron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M is a metal out of the following group:iron, nickel, cobalt or an alloy on the basis of one of the metals ofthe said group, x is an atomic fraction of absorbed oxygen in theelectrolytic alloy which is within the limits of 0.01 to 0.4, y is anatomic fraction of absorbed hydrogen in the electrolytic alloy which iswithin the limits of 0.01 to 0.4, whereby the said electrolytic alloysimultaneously fulfils the functions of both current-carrying collectorand of active material participating in the processes of redoxcharge-discharge reactions of negative electrode.
 14. Theelectrochemical energy storage device according to claim 13characterized in that for the negative electrode atomic fraction y ofabsorbed hydrogen in the electrolytic alloy is preferably within thelimits of 0.05 to 0.4.
 15. An electrochemical energy storage device ofhigh specific power containing at least one negative and one positiveelectrodes submerged in aqueous alkaline electrolyte and separated witha layer of ion-conductive but non electron-conductive material, wherebyeach electrode contains an active element interacting with theelectrolyte in the process of charge-discharge redox reactionscharacterized in that active element of positive electrode is made of anelectron-conductive electrolytic alloy having compositionM_((l-x-y))O_(x)H_(y), where M is nickel or an alloy on the basis ofnickel, x is an atomic fraction of absorbed oxygen in the electrolyticalloy being within the limits of 0.01 to 0.4, y is atomic fraction ofabsorbed hydrogen in the electrolytic alloy being within the limits of0.01 to 0.4, whereby the said electrolytic alloy simultaneously fulfilsthe functions of both current-carrying collector and of active materialparticipating in the processes of redox charge-discharge reactions ofpositive electrode.
 16. The electrochemical energy storage deviceaccording to claim 15 the electrolytic alloy is preferably within thelimits of 0.05 to 0.4.